How do the Sudanic savanna and the Guinea Coast differ in rainfall?

In western Africa, rainfall patterns are primarily dictated by the seasonal migration of the intertropical convergence zone (ITCZ) and the interplay between moist maritime air and the dry harmattan wind.123

The Guinea Coast generally experiences higher and more consistent annual precipitation than the Sudanic savanna regions. Coastal areas often receive significant rainfall, sometimes exceeding 80 to 100 inches (2,000 to 2,500 mm) annually, and typically feature two distinct rainy seasons.241

In contrast, the Sudanic savanna zone is characterized by a more pronounced moisture deficit due to a longer, more intense dry season. While annual rainfall in Sudanic areas can vary significantly from north to south—ranging from approximately 30 to 55 inches (750 to 1,400 mm)—it is generally lower than that of the coastal forest regions. The savanna climate is defined by a single, shorter wet season, making the region more susceptible to seasonal drought compared to the more humid Guinea Coast.234